Mineral districts presented herein and delineated on the enclosed map were defined according to geological criteria. The principal goal was to arrange known metallic mineral occurrences into discreet metallogenic systems of similar age and style of mineralization. It Is strongly stressed that many of the metallic occurrences have poorly understood geological controls and hence, many of the district boundaries will change as knowledge of both their deposits and geologic settings is improved. Nevertheless, this map initiates a geological approach to the subject of mine district definition and suggests that mineral districts are ultimately geological phenomena. Include a map sheet showing the distribution of metallic mineral districts of Arizona, map scale 1:1,000,000.